AZ31B镁合金TIG和MIG焊接接头组织性能比较分析

研究了AZ31B镁合金钨极氩弧焊(TIG)和熔化极氩弧焊(MIG)焊接接头组织及性能。在厚度为8.0 mm的AZ31B镁合金板材上分别进行了填丝TIG和MIG两种焊接试验,分析了AZ31B镁合金两种焊接工艺以及接头焊缝的微观组织和显微硬度。试验结果表明,填丝TIG焊缝成形良好;MIG焊接时有飞溅现象,焊缝成形不及TIG均匀。TIG和MIG焊接接头的相组成与母材的相组成一致。MIG焊接热影响区HAZ的晶内析出相弥散分布,焊缝区晶界析出相连续分布;而且MIG焊接接头的显微硬度值较TIG焊接时要高,焊接接头的力学性能有所提高。     

连续Nd：YAG激光器腔长与扩束系统对输出功率的影响

为了提高激光器输出功率,优化激光器结构尺寸和扩束系统是提高固体Nd:YAG激光器输出功率的两个重要因素.通过选择和优化激光器腔长与反射输出镜透过率的不同组合,实验测试表明,激光器腔长与输出镜透过率的最佳组合参数为L1=L2=140 mm ,T＝40%,激光器的斜率效率为4.5%.设计了凹凸透镜组合和扩束比为3倍的扩束系统.通过分析热传导在扩束系统中的作用过程,计算出扩束比与连续Nd:YAG激光器功率数学关系和扩束系统镜片的传热系数.使激光器最大输出功率比设计理论值增加25W左右.     

激光与空气等离子弧切割镁合金的试验研究

利用高功率固体脉冲Nd:YAG激光和空气等离子弧对4 mm厚的AZ31镁合金板进行了切割试验.通过光学显微镜观察分析切缝及断面的宏观形貌和微观组织,结果表明:激光切缝窄细平直,断面波纹小且分布规律;空气等离子弧切缝较宽,且切割断面容易氧化.两种方法切割镁合金断面都形成有重熔层,激光切割重熔层厚而致密,与母材交界处无明显的热影响区;空气等离子弧切割重熔层较薄,内部有大量气孔和残渣,切缝中、下部有明显的热影响区,最宽处达50μm.为提高镁合金切割加工质量提供理论依据.     

Effect of environmental media on ablation rate of stainless steel under femtosecond laser multiple raster scans

We investigate the influence of environmental media on ablation rate of AISI 443 stainless steel under femtosecond(fs) laser single raster scan and multiple raster scans in air, water, and methanol. Meanwhile, the development of ablation rate with the change of fs laser-induced surface morphology in the three environmental media is comparatively studied. The results show that environmental media as well as fs laser-induced morphology control the ablation rate with the increasing number of raster scans(N). Under single raster scanning(N = 1), the ablation rate is higher in liquid than in air due to the confinement of plasma, laser-induced shockwaves, and bubble-related mechanical forces. However, under multiple raster scans, the variation in ablation rate with the increase in N in these three environmental media is complicated and is largely determined by the surface morphology induced by previous fs laser ablation. When N > 20, the ablation rate is much higher in air than in liquids due to preferential ablation caused by the formation of nanostructures-textured mound-shaped microstructures in air. Besides, the redeposition of ejected ablated materials is also an important factor that affects the ablation depth.     

带有中间过渡层的Si3N4/Q235钎焊接头残余应力数值模拟

应用有限元软件ANSYS，对带有中间过渡层的Si3N4陶瓷与Q235金属钎焊接头的残余应力进行了三维有限元分析。分析了从高温1053K冷却到室温时接头残余应力的大小和分布情况，讨论了被连接材料本身结构形状尺寸、过渡层性能与厚度等因素对残余应力的影响规律，比较了有过渡层的方棒接头试件和圆棒接头试件残余应力的特征。这些分析结果，为工程实际提供有意义的参考。     

Al2O3陶瓷表面二元离子复合渗镀Ni-Ti合金化研究

运用多元离子复合渗镀合金的方法,采用自制的二元复合靶对Al2O3陶瓷表面进行Ni-Ti复合渗镀,实现了Al2O3陶瓷表面的合金化。采用EDS,SEM,XRD分析方法和声发射划痕试验对Al2O3陶瓷表面的沉积层进行了分析,研究了沉积层成分、物相以及界面结合强度。结果表明,沉积层中含有镍、钛、铁等元素,各元素分布较为均匀,没有明显的成分聚集现象;沉积层由镍钛的氧化物Ni[TiO3]、镍钛化合物Ni4Ti3、镍单相组成。沉积层与Al2O3陶瓷基体界面成分过渡连续,没有显著的微观和宏观缺陷;声发射划痕实验结果表明,沉积层与陶瓷基体结合得较好,在100N的最大载荷下,沉积层没有出现剥离和崩落现象。这一方法为Al2O3陶瓷表面合金化提供了新的途径。